Flavohemoglobin denitrosylase catalyzes the reaction of a nitroxyl equivalent with molecular oxygen

Alfred Hausladen, Andrew Gow, Jonathan S. Stamler

Результат исследований: Материалы для журналаСтатья

128 Цитирования (Scopus)

Выдержка

We have previously reported that bacterial flavohemoglobin (HMP) catalyzes both a rapid reaction of heme-bound O2 with nitric oxide (NO) to form nitrate [HMP-Fe(II)O2 + NO → HMP-Fe(III) + NO3 -] and, under anaerobic conditions, a slower reduction of heme-bound NO to an NO- equivalent (followed by the formation of N2O), thereby protecting against nitrosative stress under both aerobic and anaerobic conditions, and rationalizing our finding that NO is rapidly consumed across a wide range of O2 concentrations. It has been alternatively suggested that HMP activity is inhibited at low pO2 because the enzyme is then in the relatively inactive nitrosyl form [koff/kon for NO (0.000008 μM) ≪ koff/kon for O2 (0.012 μM) and KM for O2 = 30-100 μM]. To resolve this discrepancy, we have directly measured heme-ligand turnover and NADH consumption under various O2/NO concentrations. We find that, at biologically relevant O2 concentrations, HMP preferentially binds NO (not O2), which it then reacts with oxygen to form nitrate (in essence NO- + O2 → NO3 -). During steady-state turnover, the enzyme can be found in the ferric (FeIII) state. The formation of a heme-bound nitroxyl equivalent and its subsequent oxidation is a novel enzymatic function, and one that dominates the oxygenase activity under biologically relevant conditions. These data unify the mechanism of HMP/NO interaction with those recently described for the nematode Ascaris and mammalian hemoglobins, and more generally suggest that the peroxidase (FeIII)-like properties of globins have evolved for handling of NO.

Язык оригиналаАнглийский
Страницы (с-по)10108-10112
Число страниц5
ЖурналProceedings of the National Academy of Sciences of the United States of America
Том98
Номер выпуска18
DOI
СостояниеОпубликовано - 28 авг 2001
Опубликовано для внешнего пользованияДа

Отпечаток

Nitric Oxide
Oxygen
Heme
Nitrates
flavohemoglobin denitrosylase
nitroxyl
Oxygenases
Globins
Enzymes
NAD
Peroxidase
Ligands

ASJC Scopus subject areas

  • Genetics
  • General

Цитировать

Flavohemoglobin denitrosylase catalyzes the reaction of a nitroxyl equivalent with molecular oxygen. / Hausladen, Alfred; Gow, Andrew; Stamler, Jonathan S.

В: Proceedings of the National Academy of Sciences of the United States of America, Том 98, № 18, 28.08.2001, стр. 10108-10112.

Результат исследований: Материалы для журналаСтатья

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AB - We have previously reported that bacterial flavohemoglobin (HMP) catalyzes both a rapid reaction of heme-bound O2 with nitric oxide (NO) to form nitrate [HMP-Fe(II)O2 + NO → HMP-Fe(III) + NO3 -] and, under anaerobic conditions, a slower reduction of heme-bound NO to an NO- equivalent (followed by the formation of N2O), thereby protecting against nitrosative stress under both aerobic and anaerobic conditions, and rationalizing our finding that NO is rapidly consumed across a wide range of O2 concentrations. It has been alternatively suggested that HMP activity is inhibited at low pO2 because the enzyme is then in the relatively inactive nitrosyl form [koff/kon for NO (0.000008 μM) ≪ koff/kon for O2 (0.012 μM) and KM for O2 = 30-100 μM]. To resolve this discrepancy, we have directly measured heme-ligand turnover and NADH consumption under various O2/NO concentrations. We find that, at biologically relevant O2 concentrations, HMP preferentially binds NO (not O2), which it then reacts with oxygen to form nitrate (in essence NO- + O2 → NO3 -). During steady-state turnover, the enzyme can be found in the ferric (FeIII) state. The formation of a heme-bound nitroxyl equivalent and its subsequent oxidation is a novel enzymatic function, and one that dominates the oxygenase activity under biologically relevant conditions. These data unify the mechanism of HMP/NO interaction with those recently described for the nematode Ascaris and mammalian hemoglobins, and more generally suggest that the peroxidase (FeIII)-like properties of globins have evolved for handling of NO.

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